In a pathological diagnosis, a tissue section is fixed to a glass slide and a preparation is fabricated through a staining process and a sealing process. In general, when a storage term of the preparation becomes long, visibility of the preparation with the microscope deteriorates due to deterioration and color failure of a biological sample. Although there is a case in which a microscopic examination is performed to the preparation in facilities other than the facilities such as a hospital at which this is fabricated, the preparation is delivered by post in general and it takes a certain time.
In view of such circumstances, a device of saving the biological sample as image data is proposed (for example, refer to Japanese Patent Application Laid-Open No. 2009-175334). In this device, focusing technology to focus on the biological sample based on contrast of the imaged image is adopted.
The biological sample has a thickness. Therefore, in the above focusing technique, a process to shift a focal point at predetermined intervals in a depth direction of the biological sample, thereby searching an optimal focal position based on the contrast of the imaged image at the focal points is necessary.
For example, when the thickness of the biological sample on the preparation is 10 μm and a depth of field of an optical lens to condense light at the biological sample is 1 μm, a process to search the optimal focal position from approximately 50 imaged images is necessary.
This takes considerable time until focusing, and efficiency of obtaining the biological sample as the image data significantly lowers.
In light of the foregoing, it is desirable to propose the focusing device, the focusing method, the focusing program and the microscope capable of improving the efficiency of obtaining a subject image.
The distance for each pixel between one image and the other image of the phase contrast images corresponds to information indicating irregularity of an imaging area (area appearing on the image forming surface of the object lens). Since the depths of field of the separator lenses are made larger than that of the object lens by the openings in the present disclosure, detailed irregularity of the subject may be recognized before focusing from the phase contrast images. Furthermore, the detailed irregularity of the subject may be recognized before focusing and by one imaging.
Therefore, it is possible to appropriately determine the focusing position at which an entire subject appearing on the image forming surface of the object lens becomes sharp and the number thereof in consideration of the irregularity of the subject and the area according to the depth of field of the object lens in the present disclosure.
As a result, the focal position may be determined at high speed and without loss according to the subject in the imaging area as compared to a method of imaging while shifting the focal point at predetermined intervals in the depth direction of the tissue section and searching the focal position based on the contrast of the imaged image. Therefore, the focusing device, the focusing method, the focusing program and the microscope capable of improving the efficiency of obtaining the subject image may be realized.